In operations for the production of oil or gas from reservoir at a remote location, such as an offshore reservoir, it is common practice to produce hydrocarbon fluid from one or more wells to a production platform located at the site of the wells. The production platform can be fixedly installed on the seabed, such as a jack-up platform or a gravity based platform, or it can be floating at the sea surface, such as a floating production storage and offloading (FPSO) vessel. Generally, one or more wells are drilled into the reservoir from directly below the platform, and hydrocarbon fluid is produced from the wells through risers extending between the seabed and the platform. Most offshore fields also involve one or more satellite wells located at a distance from the platform and tied to the platform by pipelines on the seabed.
Offshore platforms, especially those in deep water, attribute considerably to the costs of exploiting offshore hydrocarbon reservoirs. In some instances, installing an offshore platform may even be prohibitive to economical exploitation of the reservoir. In view thereof it has been proposed to use relatively small subsea production systems instead of fixed or floating platforms for producing oil or gas from offshore fields. Such subsea systems are arranged to receive hydrocarbon fluid from one or more wells to initially separate the produced stream into a gas stream and a liquid stream, and to pump the separated streams to an onshore production facility. Alternatively the produced fluids can be transported in multi-phase flow from the subsea system to an onshore facility through a single pipeline, hence without initial separation of gas from liquid.
Although conventional technologies can be applied for the exploitation of some remote hydrocarbon fluid reservoirs, a variety of applications require improved systems and methods to produce hydrocarbon fluid in an economical way. For example, the production of hydrocarbon fluid from reservoirs located below Arctic offshore waters can prove difficult, if not impossible, with conventional technologies. Generally Arctic conditions prohibit continued operation of offshore facilities throughout the year, for example because the sea is frozen a large part of the year. For this reason, conventional offshore drilling and/or production platforms are considered inadequate for continued operation throughout the year in Arctic conditions. Moreover, exposure of pipelines to scouring from floating ice and/or hazards associated with unstable permafrost, can be prohibitive.
US patent publication 2004/0079530 discloses a wellbore system whereby a multilateral well is drilled into an offshore hydrocarbon reservoir from an first surface location vertically above the reservoir, and whereby a second well is drilled from a second surface location horizontally displaced from the first surface location. The second well extends inclined or horizontally in the direction of the multilateral well and is fluidly connected to a branch of the multilateral well. In use hydrocarbon fluid is produced from the reservoir, through the multilateral well and through the second well, to a production platform at the second surface location. However, the known wellbore system is only feasible if the second surface location is located not too far away from the hydrocarbon reservoir. The reason is that the depth at which inclined or horizontal wellbores can be drilled is limited due to anticipated problems such as low weight on bit, insufficient wellbore cleaning, differential sticking and high frictional forces acting on the drill string.
Accordingly there is a need for an improved wellbore system for the production of hydrocarbon fluid from a reservoir at a remote location, which overcomes the problems of the know system.